Hand-Held Power Tool Driven By A Flow Medium

ABSTRACT

Disclosed is a hand-held power tool with a housing ( 12 ) and a tool ( 70 )—a cutting tool, in particular—located thereon in a manner which allows it to be driven in a rotating and/or oscillating manner, it being possible to operate the tool ( 70 ) using a suction air flow, via a vacuum cleaner, in particular; the hand-held power tool is made particularly robust and safe against becoming clogged with chips by the fact that it is driven by a turbine ( 36 ) with a rotatable turbine wheel ( 38 ) and a stationary turbine housing ( 60 ); means ( ) are located between the turbine wheel ( 38 ) and the turbine housing ( 60 ) for carrying away dust and chips which accidentally enter this space.

The present invention is directed to a hand-held power tool driven by aflow medium, according to the preamble of Claim 1.

U.S. Pat. No. 6,347,985 B1 makes known a hand-held power tool which isdriven solely via the suction air flow of a vacuum cleaner. The core ofthe known hand-held power tool is a conventional Pelton turbine whichuses the suction air from the vacuum cleaner to rotate the drivenspindle and, therefore, to drive the tool. The efficiency and robustnessof the known hand-held power tools with axial and Pelton turbines—alsoreferred to as drag-type rotors—which provide mechanical power to ashaft solely via air impulses are not capable of meeting the highdemands placed on the output and suction power of these hand-held powertools which can be operated using commercial vacuum cleaners. Inparticular, particles drawn in with the suction airstream can enter thenarrow air gap between the turbine wheel and the turbine housing, whichexists due to the design. Coarse particles are unable to escape. If theyaccumulate, they can jam the turbine and impair its performance.

ADVANTAGES OF THE INVENTION

The advantage of the present invention which has the features listed inClaim 1 is that a material-removing, hand-held power tool—designed as asander or a milling machine, in particular—which does not include anelectric motor is that it is driven by a turbine which can only beoperated with suction air, e.g., from a vacuum cleaner, and whichincludes a rotatable turbine wheel and a stationary turbine housing.Means are located between the turbine wheel and the turbine housing tocarry away particles such as dust and chips which accidentally enterthis space. The present invention is highly efficient and robust for itsintended use. As a result, a particularly high portion of flow energyfrom the intake and blast air can be converted to mechanical power. Itis also ensured that sanding, milling, drilling, etc., operations whichproduce nearly no dust in the surroundings can be carried out, whiledust particles forming during the sanding process are removedcontinually, thereby combining a high rate of material removal withhighly effective suctioning away of grinding dust. In short, aparticularly advantageous type of turbine is created, which is basicallya cross between a classical direct-flow radial turbine and an axialturbine, and which is designed as a diagonal-flow radial turbine. Itcombines the advantage of minimal power loss with the advantage ofincreased energy yield from the airstream and therefore serves as ahighly effective drive for air-moving power tools. The risk associatedwith the outgoing air which drives the turbine by flowing through it andwhich contains particles is offset by certain means. These means arelocated between the turbine wheel and the turbine housing and serve tocarry away or allow the exit of wayward dust and chip particles whichleave the main airstream and enter the spaces between the moving partsof the turbine, thereby threatening to impair their motion.

Given that the means are designed, at the least, as an opening whichpasses through the turbine housing close to the inflow point of thedrive air, the particles can leave the turbine via a short path, withoutcausing any noticeable blocking or braking effects. By providingopenings in the side of the housing which have special shapes andlocations, it is possible to direct coarse particles, in particular,radially—due to their direction of motion—out of the gap between theturbine wheel and the turbine housing before they can create a jam.

Given that the means described above are also formed via surfacerecesses and/or an increased surface roughness of the turbinewheel—adjacent to the opening of the turbine housing in particular—whichserve to carry the particles along and create a preferably pulsingairstream toward the opening described—in order to blow the particlesthrough this opening, continual particle removal is improved, and therisk of the turbine wheel becoming jammed with the turbine housing isreduced further.

Given that a stationary guide-blade row is located in front of theturbine wheel and serves as a bearing seat for a pivot bearing of thedrive shaft of the turbine wheel, it performs the function of supportingthe housing structure of the hand-held power tool, which allows themanufacturing costs of the hand-held power tool to be kept particularlylow.

Given that the drive is composed only of lightweight plastic parts, thehand-held power tool is particularly lightweight and easy to handle.

Given that the hand-held power tool is provided with a wireless switchwith which the vacuum cleaner can be turned on and off, convenient andeasy operation of the hand-held power tool and the vacuum cleaner ismade possible.

Given that the rotational speed of the hand-held power tool is regulatedusing an adjustable air flap, it is possible to adapt the machine speedto the particular working conditions in an easy, cost-effective mannerusing simple means.

Given that the housing of the hand-held power tool is composed oftubular parts which can be connected with each other using a flange, itis particularly dimensionally stable, robust, and lightweight.

DRAWING

The present invention is explained below in greater detail withreference to an exemplary embodiment and the drawing.

FIG. 1 shows a longitudinal cross section of a finishing sander

FIG. 2 shows a longitudinal cross section of the turbine withguide-blade row for driving the finishing sander

FIG. 3 is a side view of the turbine in FIG. 2

FIG. 4 is a sectional side view of the turbine, with turbine housing

FIG. 5 is a top view of the turbine wheel, with turbine housing

FIG. 6 is an oblique view of the turbine wheel, with turbine housing

FIG. 7 is a top view of the turbine housing

FIG. 8 is a top view of the turbine wheel

FIG. 9 is a side view of the chip outlet in the turbine housing

FIG. 10 is a top view of the chip outlet in the turbine housing

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENT

FIG. 1 shows a hand-held power tool 10 designed as a finishing sander,in a view of the interior of housing longitudinal shell 14. Itforms—together with a second, not-shown, essentially symmetrical housingshell—a bell-shaped housing 12 with a normal axis 13. Housing 12 isjoined by connecting the two housing shells using screws which passthrough the outer, not-shown housing shell from the outside and can bescrewed into screw mandrels 35, thereby holding the two housing shellstogether at a vertical joint. On its top side 20, housing 12 transitionsinto a hollow cylindrical handle 16 which projects transversely fromnormal axis 13 and serves as suction air outlet 18. An air flap 22 ismounted on top side 20 of housing 12, which opens or closes an opening24 to flow channel 26 inside housing 12, to regulate the air intake asnecessary. To this end, a region 86 of a channel wall 28 located closeto opening 24 is perforated, so that the suction air can communicatewith the outside air in tubular flow channel 26. Channel wall 28 is heldon housing shells 14 via support ribs 30. Support ribs 30 are connectedwith reinforcement ribs 32 inside housing shell 14 and, via these, withthe outer wall of the housing and housing shell 14. As a result, airchannel 26 and channel wall 28 are reinforced, and, in particular, theyare stabilized against vibrations and resonances with the suction airwhich flows through.

At the bottom, housing 12 terminates in a straight, circumferentiallower edge 34, whose perpendicular projection downward forms a trianglewith outwardly arched sides. A sanding disk 70 is located parallel withlower edge 34 and is connected with housing 12 in an elastically movablemanner via elastic, oscillating body 75. Sanding disk 70 extends withits U-shaped base surface outwardly past the triangular, perpendicularlydownwardly projected contour of lower edge 34 and has retaining means onits underside for accommodating a not-shown sanding pad. It can bedriven in an orbital manner via a drive shaft 72 and an eccentric whichis non-rotatably mounted on its end and is not described further, sothat each point of the sanding disk and, therefore, every individualsanding grain of the sanding disk forms small circles, i.e., the typicalsanding pattern created by an orbital sander.

Drive shaft 72 is driven in a rotating manner via a turbine wheel 38 ofan air-drivable turbine 36, and is rotatably supported in housing 12 andin guide-blade row 74 via an upper and lower roller bearing 64, 66 andengages with its lower end in a third roller bearing 68 which isnon-rotatably mounted via its outer ring in sanding disk 70. Betweenlower and third roller bearing 66, 68, drive shaft 72 is non-rotatablyconnected with a balancing mass 78 which serves to compensateimbalances, in order to cancel out oscillations of eccentrically movedsanding disk 70 far away from housing 12.

An upwardly projecting annular profile 80 is formed on the top side ofbalancing mass 78, which faces guide-blade row 74. It is enclosed by anannular groove 82 with slight clearance located in the closely adjacentunderside of guide-blade row 74 and, together with annular profile 80,forms a lower, meander-like labyrinth seal 84. This prevents dust andchips from entering the gap or being moved to lower bearing 66 by thevacuum in the cavities in hand-held power tool 10, and between balancingmass 78 and guide-blade row 74 in particular. As such, the gap and lowerbearing 66 are protected for a long period of time.

Drive shaft 72 is non-rotatably enclosed in the center by turbine wheel38, thereby creating an inner, form-fit connection between the two partsvia a knurl 73 in a defined circumferential region approximately in thecenter of drive shaft 72, in the recesses of which liquid plastic entersduring the casting process, thereby creating the connection.

Turbine wheel 38 has a bell-shaped outer contour. A guide-blade row 74with lattice blades 75—which is non-rotatably held and can be clampedbetween housing shells 14—abuts lower edge 34 axially downwardly.Lattice blades 75 are designed as plastic strips mounted on their narrowside, similar to wheel blades 42 of turbine wheel 38. Guide-blade row74, which is designed as a short truncated cone, is at least partiallyenclosed on the outside by turbine housing 60—which is alsonon-rotatably supported in housing 12, at a distance equal to the heightof lattice blades 75, thereby forming a lower continuation of annularflow channel 49 of turbine wheel 38, through which the suction air isdrawn and directed. Via lattice blades 75, the suction air which flowsin from the bottom to drive turbine wheel 38 in its direction of flow,and/or the suction air from flow channel 49 or wheel blades 42 ofturbine wheel 38 is directed and its swirling is eliminated, therebyimproving the efficiency of turbine 36 considerably, especially on theinput side. Guide-blade row 74 forms—with a central recess 76 on itsunderside—a bearing seat for a bearing 66 of lower region of drive shaft72, which fixes drive shaft 72 in position in housing 12 and guides it.

Turbine housing 60 encloses—with an annular groove 57 in its upperregion—the outside of turbine wheel 38 and its annular sealing ridge 56with a certain gap distance and forms an upper labyrinth seal 51 there.An opening 102 (FIG. 5) is located on each of two diametrically opposedsides in turbine housing 60 close to annular groove 57 so that waywardchips and dust particles which enter the region between the outside ofturbine wheel 38 and turbine housing 60 can therefore exit as quickly aspossible without braking or blocking turbine wheel 38. The unwelcomeparticles can be pushed out of these openings 102 via the mechanicaltransfer effect of turbine wheel 38 and via an airstream in addition tothe suction airstream which drives the turbine, which is produced in thegap between turbine wheel 38 and turbine housing 60 via the design ofthe outer surface of turbine wheel 38 in the region of openings 102 whenturbine wheel 38 rotates.

FIG. 2 shows a longitudinal cross section of turbine wheel 38 withguide-blade row 74—which terminates axially downwardly and is fixed inposition in housing 12—as an isolated component, while it is showninstalled in FIG. 1. A support cone 48 which is shaped like a truncatedcone and is arched outwardly—similar to the cone of a juice squeezer—isshown, on which a large number of wheel blades 42 is mounted, which areshaped like flat plastic strips mounted in an upright position via theirnarrow sides on support cone 48, and the height of which increasesgradually in the direction toward the—virtual—cone peak. A cover cone 44which extends nearly in parallel with support cone 48 and the upperedges of wheel blades 42 is joined via wheel blades 42. As a result, aflow channel 48 with an annular cross section is formed between supportcone 48 and cover cone 44. It is subdivided by wheel blades 42 into alarge number of winding, individual channels, into which the suction aircan flow with particularly low flow resistance to drive turbine 36. Thelower edge of support cone 48 is tilted at an angle of approximately 45°to the cone axis and extends at an angle of approximately 90°transversely to the cone axis, unlike conventional radial turbines. Witha particularly favorable exemplary embodiment of turbine 36, the inflowangle of the blades is 40°, and their outflow angle is 30°. As indicatedby directional arrow 62, the air which flows along wheel blade 42 isredirected by 45° relative to axis 40. The redirection transverse to theplane of the drawing is not yet taken into account.

In the region of virtual cone peak 46, cover cone 44 abuts channel wall28 of air channel 26 with minimal clearance; the suction air is guidedaerodynamically through air channel 26 toward the vacuum source, i.e.,toward the vacuum cleaner.

Support cone 48 or truncated cone of turbine wheel 38 is penetrated by acentral hollow cylinder 54 which accommodates shaft 72. At the top, inthe region of a virtual cone peak, hollow cylinder 54 forms aprojecting, annular collar 52. Hollow cylinder 54 therefore attains alength such that drive shaft 72—with a defined axial extension and adefined region of its knurl 73—is positioned securely relative to theturbine wheel via this knurl 73 in the interior of hollow cylinder 54and is enclosed by it, thereby resulting in reliable rotation betweenturbine wheel 38 and drive shaft 72.

Cover cone 44—which is designed as a truncated cone and with a concavearch which increases in the direction toward a virtual tip—includes anannular sealing ridge 56 in the lower one-third of its height, on itsoutside. It is provided for axial engagement in an enclosing annulargroove 57 located on the inside of shell-like turbine housing 60 whichfaces turbine wheel 38 by extending over sealing ridge 56 as an upperlabyrinth seal 51, and prevents pressure losses inside turbine 36,therefore increasing its efficiency considerably.

To operate hand-held power tool 10, air is suctioned at suction airoutlet 18 and flows from the outside through suction holes 71 in sandingdisk 70 and between the top side of sanding disk 70 and lower housingedge 34. The air drawn in from the outside enters annular channel 49 ofguide-blade row 74 and travels further into the annular channel ofturbine wheel 38.

If radial turbine wheel 38 and guide-blade row 74 come in contact withabrasive, dusty air, they can become worn and dust can deposit there,which can negatively affect the power and service life of the drive. Toprevent this, the surfaces which come in contact with suction air aredesigned with slight, regular, golf ball-type recesses in particular, sothey have low flow resistance and increased surface strength.

In the side view of turbine 36—from FIG. 2—shown in FIG. 3, one can seeturbine housing 60 with one of the two openings 102. Turbine housing 60shown in FIG. 1 is retained non-rotatably in housing 12 and is locked inposition or clamped on support ribs 30 and extends past guide-blade row74 and turbine wheel 38 closely or with clearance, and forms upperlabyrinth seal 51 described above.

With a not-shown exemplary embodiment of the hand-held power tool—whichis similar to the exemplary embodiments described above—a wirelessswitch is mounted on the housing, which communicates with a matchingswitch assigned to the vacuum cleaner, and which can be used to turn thevacuum cleaner and, therefore, the hand-held power tool, on and off in aconvenient, cost-favorable manner.

Unlike a classical radial turbine, the air which flows through hand-heldpower tool 10 does not flow purely radially inwardly before it isredirected axially in turbine 36. Instead, it flows in the guide-bladerow and in the radial turbine at an angle of 45° relative to normal axis40 (see FIG. 2). The advantage of this oblique flow is that theefficiency of the turbine is increased markedly, since the loss ofpressure inside turbine 36 and guide-blade row 74 is minimized. Theinflow angle of the blades is 60°, and the outflow angle is 30°, inorder to also keep the outflow losses as low as possible. The angles forthe inflow region can vary between 0° and 70°, and the angles in theoutflow region can vary between 10° and 60°. The angle is selecteddepending on the quantity of air and the rotational speed expected. Thepurpose of guide-blade row 74 is to provide the airstream with thegreatest amount of pre-rotation possible. For this reason, it includeslattice blades 75 with an emergent angle of approximately 80°. A slightclearance is required between guide-blade row 74 and turbine 36, so thatthe airstream can contact turbine 36 in the most ideal manner possible.An additional support ring 88 between support ribs 90 on the undersideof support cone 48 prevents a highly fluctuating and uncontrolledno-load speed of the turbine, which can be extreme (>20000 rpm), since afan effect cannot occur when ribs are positioned purely radially.Support ring 88 and support ribs 90 are sized such that they becomethinner in the radially outward direction, so that, during injectionmolding, the material can flow outwardly quickly and with low resistanceand fill all cavities in the mold.

Additional collar 52 on inner ring of turbine wheel 38 is required sothat drive shaft 72—which has been inserted and coated via injectionmolding—can be knurled in the center. For reasons of space, lowerbearing 66 is integrated directly in guide-blade row 74 and makes itpossible for hand-held power tool 10 to have a flat design.

A turbine 36 depicted spacially in FIG. 4 is composed of a turbine wheel38 which is enclosed by a turbine housing 60 which encloses aguide-blade row 74 underneath turbine wheel 38.

Three particles—which are depicted as circles—e.g., grinding dust orchips 108—are shown between turbine housing 60—shown in a partiallyexposed view—and the outer surface of turbine wheel 38. In addition,oval indentations 103 are provided on the outer surface of turbine wheel38, which can accelerate the ambient air and create a pulsing air flow,so that particles 108 wandering between turbine housing 60 and turbinewheel 38 are carried along and are preferably transported towardguide-blade row 74, so that they can join the main airstream flowingtoward the external vacuum cleaner, which serves as drive means foroperating turbine 36 and serves to remove the particles. As analternative, particles 108 can be pushed and/or blown toward openings102 (FIGS. 3, 5).

FIG. 5 shows a top view of turbine 36. Turbine wheel 38 is shown; it isenclosed in the upper region by turbine housing 60. Also shown in thefigure are the two openings 102 which pass through turbine housing 60 ontwo diametrically opposed sides in the upper region and which serve tocarry chips away, and, through openings 102, the adjacent outer side ofturbine wheel 38.

FIG. 6 shows a spacial side view of turbine 36. The same details aredepicted as in FIG. 5, but the design of keyhole-type opening 102 isillustrated more clearly. Turbine housing 60—which is designed as astepped cylinder—extends downward in four steps and expands in themanner of a bell. An opening 102 which opens in the radial and axialdirections passes through an uppermost, cylindrical step section ondiametrically opposed sides; it extends into the next conical stepsection in the axially downward direction. Opening 102 is designed inthe shape of a keyhole. It is 9 mm wide at the top, 3 mm wide at thebottom, and is approximately 15 mm tall. Its lower hole region 111 isoffset to the left as shown in the drawing, eccentrically relative toupper region 112.

Leading edge 120 of opening 102 shown at the left in the figureextends—relative to normal axis 40—upwardly and toward the outside left,angled axially (see FIG. 9, angle α), and radially outwardly, opening atan angle. Leading edge 120 therefore offers the chips which are movingoutwardly in the direction of rotation of turbine wheel 38 as indicatedby rotational-direction arrow 130 a minimal rebounding surface; thechip-removal conditions are therefore favorable.

As shown in FIGS. 5 and 7, upper region 112 of opening 102 has asemicircular contour in the horizontal cover surface ofstepped-cylindrical turbine housing 60, which is intersected byV-shaped, lower hole region 111 which extends downward toward the jacketsurface. Semicircular, upper region 112 transitions into V-shaped edges120, 121 of the abutting section—which narrows into the shape of a V—oflower hole region 111. A ramped knife edge 140 is formed in thetransition of leading edge 120 into semicircular region 112, forming anangle β; this improves the outflow of chips, because the particles arethen exposed to a minimal rebounding surface.

FIG. 7 shows a top view of turbine housing 60 with two diametricallyopposed openings 102.

FIG. 8 shows turbine wheel 38 with guide-blade row 74 located underneathand onto which turbine housing 60 can be clipped axially.

FIG. 9 shows an enlarged view of one of the openings 102 in a side viewaccording to FIG. 6. A directional arrow 160 indicates the outflowdirection of particles 108. The unevenly V-shaped contour of opening 102with upwardly angled edges is shown; a V is formed which has an acuteangle at the bottom and transitions into a more obtuse V toward the top.

FIG. 10 shows an enlarged top view of one of the openings 102, in avertical projection according to FIG. 5 or 7. Knife edge 140 is shownparticularly clearly.

Chips 108 which enter the space between turbine wheel 38 and turbinehousing 60 are guided by the angular geometry of opening 102 and itsposition in turbine housing 60 in the clockwise direction via turbinewheel 38 toward leading edge 120. From there, they are pushed or blownat an angle upwardly along leading edge 120 and, from there, radiallyoutwardly into the interior of housing 12.

Chips which flow out of housing 12 and out of openings 102 can reachnot-shown, downwardly guiding channels. Inspection flaps or openings canbe provided in housing 12 in the region of openings 102, through whichparticularly tenacious accumulations of chips can be removed by handfrom the outside.

1. A hand-held power tool with a housing (12) and a tool (70)—a cuttingtool, in particular—located thereon in a rotatable manner, it beingpossible to operate the tool (70) using a suction air flow, via a vacuumcleaner, in particular, wherein a turbine (36) with a rotatable turbinewheel (38) and a stationary turbine housing (60) is used as the drive,and means (100) are located between the turbine wheel (38) and theturbine housing (60) for carrying away particles (108), such as dust andchips, which accidentally enter this space.
 2. The hand-held power toolas recited in claim 1, wherein the means (100) are designed as at leastone opening (102) which passes through the turbine housing (60).
 3. Thehand-held power tool as recited in claim 1, wherein the means (100) aresurface recesses (103) and/or raised surface roughness in the turbinewheel (38)—adjacent to the opening (102) of the turbine housing (60) inparticular—for carrying the particles along and creating a preferablypulsing airstream toward the opening (102) to blow the particles outwardthrough this opening (102).
 4. The hand-held power tool as recited inclaim 1, wherein the turbine (36) is provided with means for eliminatingthe swirling of the inflowing and outflowing air, in particular aguide-blade row (74)—and/or a rear guide grid; the airstream flowingonto the turbine wheel (38) is forwarded or redirected at an acute angleto the normal axis (40) of the turbine wheel (38), at an angle of 50° inparticular.
 5. The hand-held power tool as recited in claim 1, whereinthe turbine wheel (38) is provided with a labyrinth seal (51) whichprotects the turbine (36) against loss of pressure.
 6. The hand-heldpower tool as recited in claim 1, wherein the guide-blade row (74)serves as a bearing seat (76) for a bearing (66) of the drive shaft(72).
 7. The hand-held power tool as recited in claim 1, wherein itincludes a balancing mass (78) which, together with structures (80, 82)of the guide-blade row (74), forms a labyrinth seal (84).
 8. Thehand-held power tool as recited in claim 1, wherein the guide-blade row(74) is installed in the structure of the housing (12) such that itreinforces it.
 9. The hand-held power tool as recited in claim 1,wherein the air for driving the turbine wheel (38) is directed from theoutside onto the turbine (36) radially outwardly in the direction ofrotation of the turbine (36), and, therefore, radially diagonally, andis subsequently drawn in temporarily axially by the outer edge of theturbine wheel (38).
 10. The hand-held power tool as recited in claim 1,wherein it is designed as a surface grinding machine, a finishing sanderin particular.
 11. The hand-held power tool as recited in claim 1,wherein downwardly guiding channels are located next to the openings(102) between the turbine housing (60) and the housing (12) for removalof the chips which exit through the openings (102).
 12. The hand-heldpower tool as recited in claim 1, wherein inspection flaps (15) foropenings are located on the housing (12) near the openings (102),through which accumulated chips can be removed by hand from the outside.